提出一种可将离面位移与面内位移分离的三维位移计算方法。在双光束电子散斑干涉系统中增加一路参考光，使这一路参考光为两光束所共用。两束光各自独立地对变形物体进行测量，分别计算相位分布，并对其中之一进行反相位计算。理论分析表明，对二路检测光所得到的相位进行相减运算，就能够较好地减少电子噪声的影响，分离面内位移场与离面位移，实现物体变形的三维测量。介绍该方法的原理，并利用典型实验证实了该方法的可行性。

A method for three-dimensional displacement measurement by separating out-of-plane displacement from in-plane displacement is presented. A reference laser beam is added to dual beam symmetric illumination electronic speckle pattern interferometric (ESPI) system and is shared by the two illumination beams. The two illumination beams are used separately in experiment for the displacement measurement. Then two phase maps, including out-of-plane and in-plane displacement, are obtained with phase shifting technique, then one of which is calculated by reversed phase calculation method. Theoretical analysis shows that subtraction of the phase maps can greatly decrease electronic noises, separate out-of-plane displacement easily from in-plane displacement and complete three-dimensiomal displacement measurement. The principle of the method is presented and proved by a typical three-point-bending experiment.